(NOTE: This talk was given in 2011, and this field of science has developed quickly since then. Read "Corrections & Updates" below for more details.) Surgeon Anthony Atala demonstrates an early-stage experiment that could someday solve the organ-donor problem: a 3D printer that uses living cells to output a transplantable kidney. Using similar technology, Dr. Atala's young patient Luke Massella received an engineered bladder 10 years ago; we meet him onstage.